spontaneous fission rate

spontaneous Adjective

— If something is spontaneous, it happens without any outside cause; nothing else makes it happen. He made a spontaneous offer to help the old lady cross the street. — If something is spontaneous, it is random. — If something is spontaneous, it happens suddenly; it happens without any warning. — If someone does something in a spontaneous way, it is done of their own free will or without making any plan to do so. — If something is spontaneous, it was made without being planted by humans; it is indigenous.

fission

— noun reproduction of some unicellular organisms by division of the cell into two more or less equal parts — noun a nuclear reaction in which a massive nucleus splits into smaller nuclei with the simultaneous release of energy

rate Noun

— Speed. A rate is how fast something happens. Something can go at a fast rate or a slow rate. The rate of water pouring out of the lake into the river is enough to make the lake empty in a year if it doesn't rain. Her heart rate is 70 beats every minute. If we keep writing pages at this rate we might have 2000 Simple English Wiktionary words by August 4.

rate Verb

— Someone rates something when they decide how much its value is (how much it's worth). I rate this book at six out of ten: it was not the best book.